I. Field of the Invention
The present invention relates generally to electro-optical systems which receive light information from parts supported on a reference surface for determining the position of the object, and more particularly, to an electro-optical system which utilizes oblique front lighting for enhancing a characteristic feature on the surface of the object.
II. Prior Art
For automated manufacturing and/or handling systems which operate on a discrete part basis, the parts or work pieces must typically be supported in a unique orientation relative to the operating system in order for the system to properly operate. In many known systems certain parts are supplied to the system in bulk containers in an unorientated relationship and must be orientated before they can be operated on in a discrete basis. While certain parts, such as screws, rivets, and the like, are often orientated by special delivery tracks, many parts, and particularly those parts of relatively large size, are not suitable for orientation by such techniques. Moreover, the delicate nature of such parts often require that they be handled on a more discrete basis.
If parts of this type are to be automatically manipulated, information must be provided to the system, or generated within the system, from which the instantaneous orientation and position of the parts may be determined so that the part may be engaged and orientated relative to the system by an automatic mechanism. One such system has been disclosed in a co-pending application entitled "Method and Apparatus for Determining the Position of a Body", Ser. No. 470,345, filed on May 16, 1974 to Jimmy A. Michaud which is of common ownership with the present invention. Briefly, in that previously disclosed system, an unorientated part is placed on a backlit presenter stage and a vidicon-type image converter generates an electric signal representative of the silhouette of the part. Control means, which may comprise a preprogrammed computer, then analyzes the silhouette of the part to determine the position of the centroid and the angular rotation of the part relative to the centroid and rotational orientation of a test part. Following these computations, the part may be manipulated or operated on as desired.
These previously known electro-optical systems, however, suffer the disadvantage that a given silhouette may not uniquely determine the face of the part being viewed. For example, a given part may have two or more faces, one of which contains a distinctive feature on its surface, in which a backlit silhouette of the part does not reveal the distinctive feature. For these parts the previously known two dimensional part identification systems are inadequate to determine the face of the part being viewed and, hence, the complete orientation of the part on the presenter stage.